1. Field of the Invention
The present invention relates to metal-containing resin particles, a metal-containing resin layer, a method of forming the metal-containing resin layer and a substrate for electronic circuit which can easily form an arbitrary electronic circuit by performing electroless plating with the metal particle as plating kernels after printing a resin which contains metal particles, for instance, by electrophotography.
2. Description of the Related Art
In a conventional method of producing a substrate for electronic circuit, a metal conductor pattern layer is formed by performing resist coating, exposure, development, etching and the like on a thin metal film. In this production process, exposure masks are needed for respective layers, which requires a plenty of times and costs of design and production thereof. Therefore, alternation or modification of a circuit pattern gives a great effect on the production period or costs of the substrate for electronic circuit
Consequently, a method of forming a metal conductor pattern layer without using an exposure mask is developed, in which an underlying pattern layer having an arbitrary pattern is printed by electrophotography using charged particles which contain metal particles in a resin as toner, and electroless plating is conducted with fine metal particles in the printed underlying pattern layer as plating kernels.
When using the electrophotography, control of the amount of electrostatic charge of toners (charged particles) is an important factor in order to consistently print a minute pattern. Especially, in the case of toner which contains metal particles in its resin, since an electrostatically charged area on the toner surface becomes small due to exposure of the metal particles being a conductor on a portion of the surface, it becomes necessary to control the charge at an appropriate level. Moreover, shape and distribution of the metal particles contained in the printed pattern greatly influences the deposition property of plating and adherent property between the metal conductor pattern layer and a base metal at the time of electroless plating.
The fine metal particles existing on a surface on which electroless plating of an underlying pattern layer is given are covered with resin immediately after the printing, and cannot sufficiently exhibit the function as a plating kernel if they are left untouched. Therefore, it is necessary to expose the fine metal particles on the surface by etching the resin covering the fine metal particles mechanically or chemically.
However, since mechanical etching is apt to actualize a problems in flatness of the substrate, it is not suitable for etching a wide area. Accordingly, chemical etching is recommended especially for such wide areas. However, in chemical etching, the solubility of resin sometimes greatly influences the adherence between the metal conductor pattern layer and the substrate after plating. For instance, when resin is not sufficiently dissolved and fine metal particles are not sufficiently exposed on the surface even when chemical etching is performed, there was a problem that a plating layer is seldom or never deposited after electroless plating.
An object of the present invention is therefore to provide metal-containing resin particles, a metal-containing resin layer, a method of forming the metal-containing resin layer and a substrate for electronic circuit, which can control the distribution of the amount of electric charge in the toner containing the fine metal powder in the resin by controlling the particle size, shape, and content of the fine metal particles contained in the resin so that a minute pattern can be formed, and further, can improve deposition property of plating in the electroless plating.
Another object of the present invention is to provide metal-containing resin particles, a metal-containing resin layer, a method of forming the metal-containing resin layer and a substrate for electronic circuit, which effectively performs electroless plating to thereby form a metal conductor pattern layer rather more uniform by forming a layer capable of easily controlling the etching thickness on the surface of an underlying pattern layer for forming the pattern.